Desert locust control in Africa by chenboying


									                                    Desert locust
                                    control in Africa

                                    A briefing for the IPM in Developing Countries Project funded by the
                                    European Commission Environment in Developing Countries budget (DGVIII)

                                    This overview aims to introduce Commission officers, delegations, and
                                    policy advisers to issues in locust control, and discusses current research
                                    and concerns among donors and locust-affected countries.

                                               Why locusts cause concern
                                               Grasshoppers are common in many parts of Africa. But locusts are
                                               unique among grasshoppers because they can undergo phase
                                               change . This means that, under certain conditions of rainfall and
                                               population density, they change their appearance and move, feed
                                               and behave as a group, with the potential to form huge swarms
                                               which can travel great distances and devastate crops. This briefing
                                               focuses on one species, the desert locust. Desert locust plagues
                                               can affect 20% of the earth’s surface across Africa, the Middle East
                                               and Southwest Asia.

                                               The problem now
                                               After the 1950s chemical pesticides raised expectations that locust
                                               plagues could be controlled by spraying breeding areas, or
                                               spraying the swarms in the air. Money was spent on chemicals,
                                               equipment, and organisational infrastructure to monitor outbreaks.
                                               But increasingly donors and locust-affected countries are
                                               questioning whether money may not be better spent in improving
                                               crop storage, or crop insurance, local food aid or other more
                                               appropriate forms of assistance.

                                               Chemical controls—do they work?
                                               Older organochlorine pesticides used to spray on locusts were
                                               hazardous to the environment. Newer pesticides can be hazardous
                                               to humans and wildlife. The FAO’s Pesticide Referee Panel provides
                                               information about recognised locust control chemicals. There is
                                               little evidence that chemical controls—as opposed to winds, rain or
                                               lack of food—have wiped out plagues. But although locusts may
                                               cause local devastation when a swarm settles, do locusts cause
                                               damage on a national scale? Attempts are now being made to
Locust swarm: drawing courtesy of
CIRAD, France.                      assess the damage caused by locusts and set this in a national context, to see
                                    whether money may be better spent in other ways.

                                    The disposal problem
                                    Donations of inappropriate or excessive amounts of pesticides have meant
                                    that a large part of the estimated 20,000 tonnes of surplus or outdated stocks
                                    in Africa result from locust control programmes.These stocks are a danger to
                                    human health and the environment.

                                    The way forward
                                    The main issues for consideration in locust control, together with the factors
                                    needed to evaluate whether control strategies will work, are explained, and
                                    Page 4 of this briefing gives contacts and further resources.
Desert locust plagues
                                Locusts                          Prevention or cure?

 can affect over 20%
                                  Migrating locust swarms        There are two views on locust control

of the earth's surface
                                  have been known since          strategies—preventing the problem at source or
                                  biblical times. Some species   trying to deal with locust swarms when they are

 ... over 65 countries
                                  have the ability to form       in the air. These different approaches arise as a
                                  swarms covering hundreds       result of the locust’s life-cycle and the habitat in

       can be at risk.
                                  of square kilometres. The      which it breeds.
                                  swarm can migrate for             The preventative approach seeks to monitor
                                  thousands of kilometres,       locust breeding areas and spray as gregarising
                                  devastating crops en route.    populations of locusts are identified. This is
         There are many different locust species. and this       difficult in practice, as many of the principal
         paper will focus on one of the principal migratory      breeding zones are difficult to reach.The cost
         species—the desert locust Schistocerca gregaria —       and effort of infrastructure and communications
         which can affect huge areas in Africa, the Middle       required is very considerable. In many areas—
         East and South-West Asia. Over 65 countries can         Mali, Niger, Chad, Ethiopia and Sudan—there is
         be at risk of swarm, invasion and breeding.             or has been until recently civil strife.
            Locusts live as solitary grasshoppers in semi-          The other approach aims to identify and deal
         desert areas. After birth the juvenile passes           with the result of the exponential increase in the
         through five instar phases, or moults, before           gregarised population that eventually leads to a
         adulthood. The juveniles are known as hoppers.          plague or swarm. This involves aerial spraying of
         Specific conditions—a combination of rainfall,          the swarm in flight, or trying to prevent crop
         population density and food—leads to a condition        damage in areas in the path of a swarm. This
         known as phase change or gregarisation . The            requires resources that can be extensively
         solitary individuals become gregarious and move         deployed at short notice. Swarms often
         and behave as a group that can increase in size         dissipate as a result of wind, rain and lack of
         dramatically. These groups are known as hopper          food, making the role of chemical controls in
         bands. Often the bands coalesce to form large           ending the swarm unclear.
         groups, leading to swarms and outbreaks.                   The most appropriate controls will therefore
                                                                 depend on whether prevention at source, or
         The problem now                                         destruction of swarms, is the objective. An
         The last major outbreak was in 1988-89, although        overview of the locust controls follows.
         a smaller outbreak threatened in 1993-94.
         Breeding areas cover the Sahel, the Arabian             Chemical controls and concerns
         peninsula, India and Pakistan. The range of locust-     Dieldrin was the first insecticide to be used on a
         affected countries is much wider. At its height, the    large scale for locust control. Dieldrin is toxic on
         1988-89 plague threatened 43 countries, one fifth       contact with the insects. It could be sprayed on
         of the world’s land mass.                               the ground from a backpack or vehicle, and by
         During the this outbreak, nearly US$300 million         air onto locust hopper bands or over the swarm
         were spent in Africa and the Arabian peninsula for      in flight. Being persistent in the environment,
         locust control. The report commissioned by the US       ground spraying onto hoppers or across their
         Congress (see Publications ) concluded that there       likely path meant that, provided they were
         was little evidence that the costs expended on          located, the hoppers were killed if they marched
         chemical controls contributed to the eradication of     across the treated ‘barrier'. Dieldrin and other
         the plague. In fact instead of turning inland from      organochlorine insecticides were eventually
         Morocco to devastate the interior of the country        banned because of persistence, environmental
         and other countries in Northern Africa, the plague      effects, and bioconcentration in fatty tissues.
         turned out to sea and ran out of food in the                Replacement insecticides included the
         Atlantic.                                               organophosphate products fenitrothion,
            Locust control has been estimated to cost more       malathion and diazinon, and the carbamates
         than US$10 million annually for all of the African      carbaryl and propoxur. These were less hazardous
         locust-affected countries. The legacy has been          to the environment but more hazardous to
         stocks of surplus or outdated pesticides.               human and animal health. They were followed by
         Consequently, the strategic aims of locust control      chemicals of the pyrethroid family such as
         need careful analysis, taking into accunt the issues    cypermethrin and lambda-cyhalothrin, and the
         below.                                                  new phenyl pyrazole fipronil. All these broad
                                                                 spectrum ‘knock-down’ chemicals are hazardous
                                                                 to non-target species, and must only be used on
                                                                 a clearly identified locust swarm target or a
                                                                 breeding site.
 Pesticides: costs and benefits
 The local devastation caused by a           150 years." Estimates of damage         shortages, national production as a
 settling swarm of locusts can be            are difficult to obtain, but there is   whole was unaffected. This may be
 very great. However, the damage at          now a recognised and authoritative      because locusts swarm in years of
 regional or national level will be          body of work indicating that            exceptional rainfall, which is one of
 nothing like so large. The German           frequently infestation has little or    the factors that produces higher
 development agency GTZ has                  no effect on the crop price or          harvests.GTZ has pioneered
 concluded that "no large scale              availability of food other than at a    research to try and estimate the
 famines have been caused by                 localised level. Senegal was            costs and losses caused by locust
 desert locusts during the last 50           afflicted with locust plagues in        infestations, examining:
 years, and in all probability there         1957, and Mali in 1986-88, but          O the area of land afflicted with
 have not been any during the last           although there were local                   locusts
                                                                                     O the value of threatened crops
                                                                                     O the potential loss of yield
                                                                                     O the effectiveness of control

                                                                                     The financial costs of locust control
                                                                                     are generally borne at the national
                                                                                     level. Indirect costs fall on health,
                                                                                     and the environment. More work is
                                                                                     needed to clarify the effect of locust
                                                                                     infestations on the local economy
                                                                                     and livelihoods.
 Desert locust (Schistocerca gregaria). (Drawing courtesy of PANOS, UK.)

                  Newer types of chemicals include growth                  natural chemicals are the 'messengers' that may
               regulators such as diflubenzuron and trifluormuron.         prevent or interfere with the phase-change
               These products interfere with the insects’                  process. This interference will cause locusts to
               development by interrupting moulting between                remain solitary, and they will not gregarise or
               growth stages. But the locusts have to be treated           swarm.
               before they reach adulthood.                                    FAO’s EMPRES scheme (see Resources ) aims
                  Commercial suppliers have an understandable              to prevent potential locust upsurges and plagues
               interest in promoting chemical use. It is, however,         by an effective monitoring, surveillance, early
               an increasing concern among donors and                      warning and control programme, together with
               regulators that chemical treatment by itself may            research on locust ecology and control. The
               not be effective in controlling locusts. Swarms             initial focus is on FAO’s Central Region of North
               cannot always be identified, they move too quickly,         and East Africa, the main source of upsurges and
               the costs of chemicals and infrastructure are great,        plagues.
               or breeding sites are inaccessible. New                         FAO’s Migratory Pest Group is the focus for
               technologies are available, as are resources to             information exchange on locust control
               assist decision-makers.                                     strategies and developments. It also operates
                                                                           the Pesticide Referee Panel, a panel of
               Current developments                                        independent experts that evaluates field data on
               New biopesticides are about to become available.            locust chemicals (including biopesticides) and

 No large scale famines
                                    These include formulations of          makes information about them available—
                                    the pathogenic fungal                  including environmental information, which had

   have been caused by
                                    pesticide Metarhizium                  until recently been lacking.
                                    flavoviride, and others based

locusts during the last
                                                                               Donors are cooperating to consider the
                                    on plant extracts are in               economic impacts of locusts, and the most cost-

50 years, and probably
                                    development. Global                    effective forms of response, including the most
                                    Information Systems based              appropriate strategic responses. Donors are are

    not during the last
                                    on satellite technology                also coordinating field research and support
                                    promise help to locate

            150 years.
                                                                           programmes. Some of the outputs are listed in
                                    swarms. There is exciting              Publications below, and are available from
                                    research on semio-chemicals            bodies mentioned in the Resources section.
                                    and pheromones: these
Key points
O   Consider the amount and area of damage threatened by locusts.
O   Clarify the objective of the action—whether it is for prevention or swarm
    control—and whether chemical treatment is appropriate.
O   Contingency planning and coordination between locust-affected areas
    and donors is vital.
O   Shared experience and expertise is available from other donors and agencies.

          Conclusions                                               Resources
          Research and technology in locust control are             Publications
          advancing. There are real prospects of biological         A Plague of Locusts—Special Report . US Congress
                                                                    Office of Technology Assessment OTA-F-450. US
          controls and better analysis of the economic costs
                                                                    Government Printing Office, Washington DC, USA.
          of locusts. If there are yet no ready-made solutions
                                                                    Desert Locust Management—A time for change.
          to swarms, there is increasingly sophisticated            S.R. Joffe. World Bank Discussion paper 284. World
          expertise available. There is no substitute for long-     Bank, Washington 1995.
          term planning to enable decision makers to deal           Desert Locust Control Using Existing Techniques—
                                                                    an evaluation of strategies . A.Van Huis. Proceedings
          with emergency problems in a strategic context.           of a Seminar held in Wageningen, Netherlands, 6-11
              A recent World Bank discussion paper (see Joffe       December 1993. Wageningen Agricultural University,
          Publications ) summed up the recommended                  Wageningen, Netherlands, 1994.

          approach to locust control: "… the need for a             Economics of Desert Locust Control. C.A. Herok, S.
                                                                    Krall.GTZ, Eschborn 1995.
          targeted, impact-oriented response to the risks
          created by locusts will shape the strategies              Organisations
          adopted. These will need to be cost-effective. A          FAO's Emergency Prevention System (EMPRES)
          balance will need to be found between the political       project provides early warning of locust upsurges in
                                                                    breeding areas. FAO’s Pesticide Referee Panel also
          pressures, which are an inevitable characteristic of      publishes data on the effects of particular pesticides
          locust management, and the realistic capacity of          and usage recommendations. Contact: Bernard
          Desert Locusts to cause economic and social               Zelazny, Locust, Migratory Pests and emergency
                                                                    Operations Group, FAO, Via delle Terme di Caracalla,
          hardship."                                                00100 Rome, Italy. Tel. +39 6 5705 53468; fax +39 6
              Contingency planning has been shown to be             5705 52271.
          important, and so has coordination between                Programme of research, information and training
          donors. Because of the mobility of locust swarms,         on desert locusts (PRIFAS). Publishes a large body
                                                                    of research and locust warning bulletins. Contact:
          it is difficult for one country alone to take effective   PRIFAS (Département GERDAT, Centre de Recher-
          action.                                                   che CIRAD, 2477 av. Du Val de Montferrand, BP
                                                                    5035, 34032 Montpellier Cedex 1, France. Tel +33 4
              Decison-makers should bear in mind a number
                                                                    67 61 58 45; fax +33 4 67 41 09 58.
          of factors which may require expert advice. These
                                                                    Deutsche Gesellschaft fur Technische
          factors include the estimated damage, and the             Zusammenarbeit (GTZ) runs research programmes
          possibility of coordination with neighbouring             including assessment of crop losses, and trials of
                                                                    new control methods. Contact: Dr Stephan Krall,
          affected areas, regional bodies and FAO's                 GTZ, OE 4232 Pflanzenschutz, Dag
          EMPRES service. There are increasing alternatives         Hammarskjoldweg 1-5, D-65760 Eschborn, Ger-
          to chemical control of locusts. Advice on                 many. Tel +49 6196 79 1428; fax +49 6196 79 7173.
          strategies, coordination and experience can be            CABI Bioscience works on the development of
                                                                    biological controls against insect pests including
          sought from the agencies and donors listed                locusts. Contact: Director, Silwood Park, Buckhurst
          opposite.                                                 Road, Ascot, Berks, SL5 7TA, UK. Tel. +44 1344
                                                                    872999; fax +44 1344 875007.

                                                                    Desert locust control in Africa, PMN No. 4, April, 1998.
                                                                    This briefing is one of a series prepared by Pesticide Action
                                                                    Network UK (PAN UK), which is responsible for its contents, as
                                                                    consultants to DGVIII of the EC. PAN UK is an independent
                            PESTICIDE                               charity working to reduce pesticide problems in developing
                                                                    countries. Its quarterly journal Pesticides News reports on
                            ACTION                                  pesticides and IPM.

                            NETWORK UK                              at Pesticide Action Network UK,
                                                                    Contact Mark Davis, Barbara Dinham or Stephanie Williamson

                                                                    Eurolink Centre, 49 Effra Road, London SW2 1BZ, UK
                                                                    Tel +44 20 7274 8895 Fax +44 20 7274 9084
                                                                    Email, Website

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